LYNN – The Water and Sewer Commission?s director said residential bills will increase by about $20 in June when commissioners meet to hike rates for the first time in three years.Daniel O?Neill said rising commission insurance costs and two large-scale projects combined with reduced money-making opportunities forced the hike.?We pushed the limit with three years, but we can?t do a fourth,” O?Neill said.O?Neill said the increase could be less than $20 over the next year for many homeowners because the current $9.45 combined rate is based on annual water use of 10,000 cubic feet. He said actual residential consumption locally is about 7,000 cubic feet translating into a $656 annual bill.Lynn is “on the medium to low side” for rates and rate increases compared to other eastern Massachusetts communities, O?Neill said.The Massachusetts Water Resources Authority?s advisory board compares rates based on 12,000 cubic feet of water use annually, and its 2013 survey indicates Lynn homeowners pay less for water and sewer compared to many of their neighbors.Lynn water and sewer bills totaled $1,137 annually, based on 12,000 cubic feet of water used. By contrast, Nahant residents paid $1,873 for water and sewer and Peabody residents paid $715.Lynn treats its water and sewage locally in plants located on Commercial Street and Parkland Avenue, but neighboring communities mostly rely on the authority for water and sewer service. Communities set local rates on top of base rates charged by the authority.?Nahant?s is almost double our rate,” O?Neill said.Commissioners are scheduled to meet on June 4 at 6 p.m. in their 400 Parkland St. meeting room to discuss rates.Peabody, Saugus and Lynn did not increase rates in 2013, according to the survey, while Revere saw a 15 percent increase and Swampscott reduced rates by almost 3 percent.O?Neill said commission water sales increased in 2010 and 2011 and when dry summers prompted residents to increase water use in gardens and on lawns. The commission also used a $7.25 million payment from a 2010 legal settlement with a former contractor to offset rates.The commission took on two major projects this year – installing a wind turbine off the Lynnway and it has started planning to meet state standards for upgrading waste incinerators.State tax dollars paid for most of the turbine work but O?Neill said the incinerator represents a looming expense. He said the cost of borrowing money to pay for major commission projects represents one-third of Water and Sewer?s $27 million budget.Water and Sewer rates rose from $3.76 since 1993. By contrast, Water Resources Authority bills climbed, according to the advisory board survey, from $559 in 1993 to a current average bill of $1,389.The last major rate increase locally occurred in 2007 and 2008 when the commission increased rates from a $7.76 combined rate to $8.66.